1. Field of the Invention
This invention relates to a bag of the type usable in microwave cooking of food products, such as popcorn. The invention also relates to a method of making a bag of the indicated type.
2. Description of the Prior Art
Microwave popcorn bags are well known. Illustrative of bags of this type are those disclosed in U.S. Pat. Nos. 3,691,374; 3,851,574; 3,973,045; 4,461,031; 4,571,337; 4,691,374; 4,892,744; and 5,044,777.
Although bags of the above-indicated types are generally satisfactory, there is a need for improvement thereof in two areas, namely, in the cost of manufacture, and in the use of microwave packages made therefrom. Present day bags of the indicated type are formed into packages containing popcorn kernels, the packages being closed at upper and lower ends thereof by means of heat seals formed by the application of heat and pressure. The use of heat seals to close both ends of the bag is the source of two problems. The first problem is that it is difficult to provide a bag making process which can operate at a high speed because the formation of a heat seal closure requires a considerable dwell time, which extends the length of the production line. Another problem is that heat seal closures are difficult to open after the microwave cooking operation in order to gain access to the cooked product.
Attempts to provide an easily openable popcorn package are disclosed in U.S. Pat. No. 4,571,337, which illustrates in FIGS. 7 and 8 the manner in which the bag is opened by pulling on the diagonally opposite corners at the upper end of a package after the microwave cooking operation is completed. The use of heat seal closure as disclosed in the U.S. Pat. No. 4,571,337, which is illustrative of the prior art, has proved to present problems in the easy opening of the bag. In many applications with the heat sealed closures of the prior art, the closure strength provided by the heat seal is greater than the tear strength of the paper forming the side panels of the bag thereby resulting in torn bags, spilled popcorn, and possible steam exposure to the consumer during the opening of the bag.